Synchrotron injector system, and synchrotron system operation method

ABSTRACT

A synchrotron injector system comprising a first ion source which generates a first ion, a second ion source which generates a second ion having a smaller charge-to-mass ratio than a charge-to-mass ratio of the first ion, a pre-accelerator having the capability to enable to accelerate both the first ion and the second ion, a low-energy beam transport line which is constituted in such a way to inject either the first ion or the second ion into the pre-accelerator, and a self-focusing type post-accelerator which accelerates only the first ion after acceleration which is emitted from the pre-accelerator.

TECHNICAL FIELD

This invention relates to a synchrotron injector system for injectingdifferent kinds of ions into a synchrotron so as to enable to acceleratedifferent kinds of ions in one synchrotron accelerator system.

BACKGROUND ART

Charged particles are accelerated by a synchrotron and a particle beam,a bundle of high-energy charged particles which are emitted from thesynchrotron, is used to treat cancer, for example. Regarding a particlebeam for medical treatment, in some cases, it is preferable to select akind of a particle beam depending on an object to be treated.Consequently, it is expected to configure one synchrotron acceleratorsystem to enable to emit different kinds of particle beams. Synchrotronsaccelerate charged particles that is, ions, which are injected, and inorder to enable to emit different kinds of particle beams, a synchrotroninjector system which injects different kinds of ions into a synchrotronis necessary.

Patent Document 1 discloses technology by which all kinds of ions can beaccelerated to desired level of energy in the same synchrotron.Regarding an injector system for injecting ions into the synchrotron, itis stated such that an ion beam which is accelerated to a given level ofenergy by a pre-accelerator is injected.

Further, in Patent Document 2, it is stated such that in order to use aproton beam together with a carbon beam, ion sources which generate eachof beams are necessary, however, the details regarding a pre-acceleratorwhich injects ions into a synchrotron are not stated.

Further, Patent Document 3 discloses the configuration in which aparticle beam such as protons of large current can be accelerated in anAPF-IH linear accelerator.

PRIOR ART REFERENCE Patent Document [Patent Document 1]

Japanese Patent Application Laid-Open No. 2006-310013 (Paragraph 0058,etc.)

[Patent Document 2]

Japanese Patent Application Laid-Open No. 2009-217938 (Paragraph 0048,etc.)

[Patent Document 3]

International publication WO2012/008255

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In a synchrotron injector system which preliminarily acceleratesdifferent kinds of ions, for example, a proton and a carbon ion so as toenable to accelerate in a synchrotron, as described in Patent Document1, different kinds of ions are accelerated to the same level of energy.As above mentioned, conventionally synchrotron injector systems are tieddown to the conditions which are the same preliminary accelerationenergy for both kinds and the same accelerator, etc. The above mentionedconventional injector systems are injector systems whose preliminaryacceleration energy is not optimum for each of kinds of ions, therefore,the injector systems are inefficient and large-sized. An ion whosecharge-to-mass ratio (charge/mass) is large (for example, aproton:charge/mass=1/1) has large space charge effect, therefore it ispreferable for incident energy to a synchrotron to be larger, incomparison with an ion whose charge-to-mass ratio is small (for example,a carbon ion:charge/mass=4/12). An ion whose charge-to-mass ratio issmall needs higher acceleration voltage to be accelerated in comparisonwith an ion whose charge-to-mass ratio is large, therefore the size ofan accelerator is larger. Consequently, it is preferable for incidentenergy to a synchrotron to be lower in comparison with an ion whosecharge-to-mass ratio is large. Conventionally, the above-mentionedproblems cannot be solved, regardless of an ion whose charge-to-mass islarge or an ion whose charge-to-mass is small, incident energy to asynchrotron is fixed to the same, and size of a synchrotron is large.

This invention is made to solve the above-mentioned problems ofconventional synchrotron injector systems, and an objective of thisinvention is to obtain a small-sized synchrotron injector system bywhich different kinds of ions can be accelerated to different levels ofenergy so as to be emitted.

Means for Solving the Problems

A synchrotron injector system of this invention is a synchrotroninjector system which emits an ion which is injected into a synchrotronand comprises a first ion source which generates a first ion, a secondion source which generates a second ion having a smaller charge-to-massratio than a charge-to-mass ratio of the first ion, a pre-acceleratorhaving the capability to enable to accelerate both the first ion and thesecond ion, a low-energy beam transport line which is constituted insuch a way to inject either the first ion or the second ion into thepre-accelerator, and a self-focusing type post-accelerator whichaccelerates only the first ion after acceleration which is emitted fromthe pre-accelerator.

Advantage of the Invention

According to this invention, a small-sized synchrotron injector systemwhich can emit different kinds of ion with different energy can beprovided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of a synchrotroninjector system according to EMBODIMENT 1 of this invention.

FIG. 2 is a block diagram showing the configuration of a synchrotroninjector system according to EMBODIMENT 2 of this invention.

FIG. 3 is a block diagram showing the configuration of a synchrotroninjector system according to EMBODIMENT 3 of this invention.

FIG. 4 is a block diagram showing the configuration of a synchrotroninjector system according to EMBODIMENT 4 of this invention.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Regarding synchrotron injector systems, accelerating a heavy ion needsgreater electric power than accelerating a light ion. Consequently,first, an accelerator which accelerates ions to the energy which isneeded by a carbon ion, that is, a heavy ion is designed. Regarding alight proton, based on ideas such that in an accelerator whichaccelerates an ion to the energy which is needed by a carbon ion, byreducing electric power, a proton can be accelerated to the same energyas that of a carbon ion, conventionally, injector systems, in which acarbon ion and a proton are accelerated to the same energy so as to beemitted, are realized. However, in a case of an ion whose charge-to-massratio is large such as a proton, it is preferable for incident energy toa synchrotron to be larger in comparison with a case of an ion whosecharge-to-mass ratio is small such as a carbon. Conventionally,designing accelerators for a heavy carbon ion is first priority,therefore, there is no ideas such that an injector system in which acarbon ion and a proton are emitted with different energy is realized bythe same injector system.

On the other hand, according to this invention, the idea such that aninjector system which is optimized for an ion whose charge-to-mass ratiois small is used to accelerate an ion whose charge-to-mass ratio islarge is abandoned, based on an idea which is opposite to conventionalideas, that is, a part of an injector system which accelerates an ionwhose charge-to-mass ratio is large to incident energy which is suitablefor a synchrotron is used for accelerating an ion whose charge-to-massratio is small, an injector system to accelerate different ions todifferent energy can be realized. According to the above-mentioned idea,regarding an ion whose charge-to-mass ratio is small and an ion whosecharge-to-mass ratio is large, an injector system whose size is small,by which suitable energy for each of the above-mentioned ions can beemitted as incident energy to a synchrotron, can be realized.Hereinafter, the details of this invention will be described referringto EMBODIMENTs.

Embodiment 1

FIG. 1 is a block diagram showing a configuration of a synchrotroninjector system according to EMBODIMENT 1 of this invention. Asynchrotron injector system 10 enables to inject two kinds of ions intoa synchrotron 7. The synchrotron injector system 10 comprises a firstion source 1 which generates a first ion and a second ion source 2 whichgenerates a second ion having a smaller charge-to-mass ratio than thatof the first ion. Hereinafter, referring to a case in which a proton isused as a first ion and a carbon ion is used as a second ion, thedetails will be described. However, any combination of a first ion and asecond ion whose charge-to-mass ratio is smaller than that of the firstion can be applied to this invention. For example, a combination of aproton as a first ion (charge-to-mass ratio=1) and a helium ion as asecond ion (charge-to-mass ratio=1/2) or a combination of a helium ionas a first ion and a carbon ion as a second ion can be applied to thisinvention.

A proton is monovalent, and when mass of a proton is 1, a charge-to-massratio of a proton is 1/1. A carbon ion is tetravalent, and when mass ofa proton is 1, mass of a carbon ion is 12, therefore a charge-to-massratio of a carbon ion is 4/12. As above mentioned, a charge-to-massratio of a carbon ion is smaller than that of a proton. A proton whichis generated by the first ion source 1 passes through a first low-energybeam transport line 41, a carbon ion which is generated by the secondion source 2 passes through a second low-energy beam transport line 42and is injected into a joining device 43. It is configured such that thefirst low-energy beam transport line 41 and the second low-energy beamtransport line 42 are joined by the joining device 43 and merge with onebeam line 44 so as for a proton or a carbon ion to be injected into apre-accelerator 5. A transport line where a proton is emitted from thefirst ion source 1 and is injected into the pre-accelerator 5 and atransport line where a carbon ion is emitted from the second ion source2 and is injected into the pre-accelerator 5 are collectively called alow-energy beam transport line 4.

In the joining device 43, a carbon ion form the second ion source 2 isdeflected so as to merge with the beam line 44. Carbon ions which areemitted from the second ion source 2 contains carbon ions havingdifferent valence except for tetravalent. In an accelerator, only carbonions which are tetravalent are accelerated. Consequently, it isconfigured such that by deflecting carbon ions from the second ionsource 2 at a part of the joining device 43, only carbon ions which aretetravalent are made to merge with the beam line 44.

The pre-accelerator 5 is configured to accelerate protons or carbon ionswhich are injected to 4 MeV/u, for example. That is, the pre-accelerator5 has an ability to accelerate both protons and carbon ions. Protons orcarbon ions which are emitted from the pre-accelerator 5 are injectedinto a post-accelerator 6. The post-accelerator 6 is a self-focusingtype accelerator which does not contain an electromagnet for convergingions such as APF (Alternating-Phase Focusing)-IH (Interdigital-H) kindlinear accelerator, etc. The post-accelerator 6 is configured toaccelerate protons, for example, from 4 MeV/u to 7 MeV/u. In a casewhere ions which are injected into the post-accelerator 6 are protons,for example, protons are accelerated to 7 MeV/u and are emitted.However, in a case where ions which are injected are carbon ions, anacceleration operation is not performed by the post-accelerator 6, andthe carbon ions are emitted with energy of 4 MeV/u as they are. Further,it is configured to inject protons with 7 MeV/u or carbon ions with 4MeV/u which are emitted into the synchrotron 7 so as to be accelerated.

As above mentioned, for example, in a case where an ion which is neededas a particle beam for medical treatment is a proton, in a synchrotroninjector system according to EMBODIMENT 1 of this invention, protons aregenerated by the first ion source 1 and are injected into thepre-accelerator 5 via the low energy beam transport line 4 and areaccelerated to energy of 4 MeV/u. The protons which are accelerated toenergy of 4 MeV/u are accelerated by the post-accelerator 6 to energy of7 MeV/u and are injected into the synchrotron 7. In the synchrotron 7,the protons are further accelerated to energy which is needed formedical treatment.

On the other hand, in a case where an ion which is needed as a particlebeam for medical treatment is a carbon ion, carbon ions are generated bythe second ion source 2 and are injected into the pre-accelerator 5 viathe low energy beam transport line 4 and are accelerated to energy of 4MeV/u. The carbon ions which are accelerated to energy of 4 MeV/u areinjected into the post-accelerator 6, however, in the post-accelerator6, the carbon ions are not accelerated and are emitted with energy of 4Mev/u as they are and are injected into the synchrotron 7. In thesynchrotron 7, the carbo ions are further accelerated to energy which isneeded for medical treatment.

As above mentioned, in a case where ions which are injected into thepost-accelerator 6 are carbon ions, an acceleration operation is notperformed by the post-accelerator 6, and the carbon ions which areinjected are passed through the post-accelerator 6 and are emitted. Thepost-accelerator 6 is a self-focusing type accelerator which does notcontain an electromagnet, therefore the carbon ions which are injectedare not influenced by a magnetic field and can be emitted as they are.Further, the post-accelerator 6 is configured so as to enable toaccelerate only protons. Consequently, in comparison with an acceleratorhaving the configuration in which carbon ions also can be accelerated,the post-accelerator 6 having the above-mentioned configuration requiresless energy and whose size can be miniaturized.

Here, it is preferable such that a beam diameter of the post-accelerator6 is made to be larger than that of the pre-accelerator 5. When a beamdiameter of the post-accelerator 6, for example, an aperture diameter ofan acceleration electrode is made to be larger than a beam diameter ofthe pre-accelerator 5, contamination which is caused by the situation,that is, carbon ions passing through in the post-accelerator 6 hit anelectrode, etc. so as to be lost, can be prevented.

As above mentioned, in a synchrotron injector system according toEMBODIMENT 1, the pre-accelerator 5 is configured so as to enable toaccelerate both a carbon ion whose charge-to-mass ratio is small and aproton whose charge-to-mass ratio is large to energy which is suitablefor a carbon ion whose charge-to-mass ratio is small as incident energyof a synchrotron, and the post-accelerator 6 is configured so as toaccelerate a proton whose charge-to-mass ratio is large to energy whichis suitable as incident energy of a synchrotron. Consequently, as aninjector which can inject two kinds of ions into a synchrotron, asmall-sized synchrotron injector system by which both of a carbon ionwhose charge-to-mass ratio is small and a proton whose charge-to-massratio is large can be accelerated to energy which is suitable asincident energy to a synchrotron and is emitted can be realized.

Embodiment 2

FIG. 2 is a block diagram showing the configuration of a synchrotroninjector system according to EMBODIMENT 2 of this invention. In the sameway as that of EMBODIMENT 1, a first ion source 1 which generates afirst ion and a second ion source 2 which generates a second ion havinga smaller charge-to-mass ratio than that of the first ion source areprovided. A proton which is generated by the first ion source 1 passesthrough a first low-energy beam transport line 41, a carbon ion which isgenerated by the second ion source 2 passes through a second low-energybeam transport line 42 and are injected into a joining device 43. It isconfigured such that the first low-energy beam transport line 41 and thesecond low-energy beam transport line 42 are joined by the joiningdevice 43 and merge with one beam line 44 so as for a proton or a carbonion to be injected into a pre-accelerator 5.

The pre-accelerator 5 is configured to accelerate protons or carbon ionswhich are injected to 4 MeV/u, for example. Protons or carbon ions whichare emitted from the pre-accelerator 5 are injected into a distributor30. In a case where ions are protons, the protons are transported fromthe distributor 30 via a deflector so as to be injected into apost-accelerator 6. The post-accelerator 6 is a self-focusing typeaccelerator which does not contain an electromagnet for converging ionssuch as APF (Alternating-Phase Focusing)-IH (Interdigital-H) kind linearaccelerator, etc. The post-accelerator 6 is configured to accelerateprotons, for example, from 4 MeV/u to 7 MeV/u.

On the other hand, in a case where ions are carbon ions, it isconfigured such that the carbon ions which are emitted from thepre-accelerator 5 pass through the distributor 30 and a joining device33 and do not pass through the post-accelerator 6, and the carbon ionsare emitted from a medium energy beam transport line 34 so as to beinjected directly into a synchrotron 7.

It is configured such that the protons which are accelerated by thepost-accelerator 6 to 7 MeV/u, for example, merge with the medium energybeam transport line 34, where carbon ions also pass through, via adeflector 32 and the joining device 33 and are injected to asynchrotron.

As above mentioned, regarding a synchrotron injector system according toEMBODIMENT 2, for example in a case where an ion which is needed as aparticle beam for medical treatment is a proton, protons are generatedby the first ion source 1 and are injected into the pre-accelerator 5via a low-energy beam transport line 4 so as to be accelerated to energyof 4 MeV/u. Protons which are accelerated to energy of 4 MeV/u areaccelerated by the post-accelerator 6 to energy of 7 MeV/u so as to beinjected into the synchrotron 7. In the synchrotron 7, the protons arefurther accelerated to energy which is needed for medical treatment.

On the other hand, in a case where an ion which is needed as a particlebeam for medical treatment is a carbon ion, carbon ions are generated bythe second ion source 2 and are injected into the pre-accelerator 5 viathe low-energy beam transport line 4 and are accelerated to energy of 4MeV/u. The carbon ions which are accelerated to energy of 4 MeV/u arenot injected into the post-accelerator 6 but are emitted from asynchrotron injector system 10 with energy of 4 MeV/u as they are andare injected into the synchrotron 7. In the synchrotron 7, the carbonions are further accelerated to energy which is needed for medicaltreatment.

As above mentioned, in a case where ions are carbon ions, it isconfigured such that the carbon ions are not passed through thepost-accelerator 6 but are accelerated by the pre-accelerator 5 so as toincrease their energy and are emitted directly from the synchrotroninjector system 10. The post-accelerator 6 is configured so as to enableto accelerate only protons, therefore, according to the above-mentionedconfiguration, in comparison with the configuration of an accelerator bywhich carbon ions also can be accelerated, the amount of electricitywhich is needed can be decreased, and the size can be miniaturized.Further, carbon ions do not pass through the post-accelerator 6,therefore contamination which is caused by the situation, that is,carbon ions passing through in the post-accelerator 6 hit an electrode,etc. so as to be lost, can be prevented.

Embodiment 3

FIG. 3 is a block diagram showing the configuration of a synchrotroninjector system according to EMBODIMENT 3 of this invention. In the sameway as that of EMBODIMENT 1 and EMBODIMENT 2, a first ion source 1 whichgenerates a proton as a first ion and a second ion source 2 whichgenerates a carbon ion as a second ion having a smaller charge-to-massratio than that of the first ion source are provided. A proton which isgenerated from the first ion source 1 passes through a first low-energybeam transport line 41, a carbon ion which is generated from the secondion source 2 passes through a second low-energy beam transport line 42and are injected into a joining device 43. A pre-accelerator comprises afront-stage accelerator 51 and a back-stage accelerator 52. It isconfigured such that the first low-energy beam transport line 41 and thesecond low-energy beam transport line 42 are joined by the joiningdevice 43 and merge with one beam line 44 so as for a proton or a carbonion to be injected into the front-stage accelerator 51.

In the front-stage accelerator 51, protons or carbon ions which areinjected are bunched. As the front-stage accelerator 51, for example, anaccelerator such as RFQ (Radio Frequency Quadrupole) is suitable.Protons or carbon ions which are bunched in the front-stage accelerator51 are accelerated in the back-stage accelerator 52 as injection energyof a synchrotron 7, for example, to energy of 4 MeV/u which is suitablefor carbon ions. As the back-stage accelerator 52, for example, anaccelerator such as DTL (Drift Tube Linac) is suitable.

In the same way as that of EMBODIMENT 1, protons or carbon ions whichare accelerated by the back-stage accelerator 52 to energy of 4 MeV/uare injected into a post-accelerator 6. The post accelerator 6 is aself-focusing type accelerator which does not contain an electromagnetfor converging ions such as APF (Alternating-Phase Focusing)-IH(Interdigital-H) kind linear accelerator, etc. The post-accelerator 6 isconfigured to accelerate protons, for example, from 4 MeV/u to 7 MeV/u.In a case where ions which are injected into the post-accelerator 6 areprotons, for example, the protons are accelerated to energy of 7 MeV/uand are emitted. However, in a case where ions which are injected intothe post accelerator 6 are carbon ions, the carbon ions are notaccelerated and are emitted with energy of 4 MeV/u as they are. It isconfigured such that protons with energy of 7 MeV/u or carbon ions withenergy of 4 MeV/u are injected into the synchrotron 7 to be acceleratedin the synchrotron 7.

As above mentioned, in a synchrotron injector system according toEMBODIMENT 3 of this invention, in a case where an ion which is neededas a particle beam for medical treatment is a proton, for example,protons are generated by the first ion source 1 and are injected intothe front-stage accelerator 51 via a low-energy beam transport line 4 soas to be bunched, and are accelerated by the back-stage accelerator 52to energy of 4 MeV/u. The protons which are accelerated to energy of 4MeV/u are further accelerated by the post-accelerator 6 to energy of 7MeV/u so as to be injected into the synchrotron 7. In the synchrotron 7,the protons are further accelerated to energy which is needed formedical treatment.

On the hand, in a case where an ion which is needed as a particle beamfor medical treatment is a carbon ion, carbon ions are generated by thesecond ion source 2 and are injected into the front-stage accelerator 51via the low-energy beam transport line 4 so as to be bunched and areaccelerated to energy of 4 MeV/u. The carbon ions which are acceleratedto energy of 4 MeV/u are injected into the post-accelerator 6 but arenot accelerated in the post-accelerator 6 and are emitted with energy of4 MeV/u as they are and are injected into the synchrotron 7. In thesynchrotron 7, the carbon ions are further accelerated to energy whichis needed for medical treatment.

As above mentioned, in a synchrotron injector system according toEMBODIMENT 3 of this invention, in the same way as that of EMBODIMENT 1,in a case where ions which are injected into the post-accelerator 6 arecarbon ions, the carbon ions are not accelerated by the post-accelerator6 but are passed through the post-accelerator 6 maintaining its energyand are emitted. The post-accelerator 6 is a self-focusing typeaccelerator which does not contain an electromagnet, therefore, thecarbon ions which are injected are not influenced by a magnetic fieldand can be emitted as they are. The post-accelerator 6 is configured soas to enable to accelerate only protons, therefore, according to theabove-mentioned configuration, in comparison with the configuration ofan accelerator by which carbon ions also can be accelerated, the amountof electricity which is needed can be decreased, and the size can beminiaturized. Here, in the same way as that which is described inEMBODIMENT 1, it is preferable such that a beam diameter of thepost-accelerator 6 is made to be larger than that of the pre-accelerator5. When a beam diameter of the post-accelerator 6 is made to be largerthan a beam diameter of the pre-accelerator 5, contamination in thepost-accelerator 6 which is caused by the situation, that is, carbonions which pass through hit an electrode, etc. and are lost, can beprevented.

Embodiment 4

FIG. 4 is a block diagram showing the configuration of a synchrotroninjector system according to EMBODIMENT 4 of this invention. InEMBODIMENT 4, in the same way as that of EMBODIMENT 3, protons or carbonions are bunched in a front-stage accelerator 51, and in a back-stageaccelerator 52, protons or carbon ions are accelerated as incidentenergy to energy of 4 MeV/u, for example, which is suitable to carbonions.

Protons or carbon ions which are emitted from the back-stage accelerator52 are injected into a distributor 30 in the same way as that ofEMBODIMENT 2. In the distributor 30, in a case where ions which areinjected into are protons, the protons are distributed so as to beinjected into a post-accelerator 6 via a deflector 31. It is configuredsuch that the protons which are injected into the post-accelerator 6 areaccelerated by the post-accelerator 6 to energy of 7 MeV/u, for example,pass through a joining device 33 via a deflector 32 and merge with amedium energy beam transport line 34 and are emitted from a synchrotroninjector system 10. On the hand, it is configured such that in a casewhere ions which are injected into the distributor 30 are carbon ions,the carbon ions are not injected into the post-accelerator 6 and areemitted from the medium energy beam transport line 34 maintaining itsenergy as they are.

As above mentioned, in a case of carbon ions, it is configured such thatthe carbon ions are not passed through the post-accelerator 6 but thecarbon ions which are accelerated by the back-stage accelerator 52 so asto increase their energy are emitted directly form the synchrotroninjector system 10. The post-accelerator 6 is configured so as to enableto accelerate only protons, therefore, according to the above-mentionedconfiguration, in comparison with the configuration of an accelerator bywhich carbon ions also can be accelerated, the amount of electricitywhich is needed can be decreased, and the size can be miniaturized. In asynchrotron injector system according to EMBODIMENT 4, in the same wayas that of EMBODIMENT 2, the carbon ions do not pass through thepost-accelerator 6, therefore contamination in the post-accelerator 6which is caused by the situation, that is, carbon ions which passthrough hit an electrode, etc. and are lost, can be prevented.

DESCRIPTION OF REFERENCE SIGNS

-   1. first ion source-   2. second ion source-   4. low-energy beam transport line-   5. pre-accelerator-   6. post-accelerator-   7. synchrotron-   10. synchrotron injector system-   30. distributor-   34. medium energy beam transport line-   43. joining device

1. A synchrotron injector system, which emits an ion which is injectedinto a synchrotron, comprising a first ion source which generates afirst ion, a second ion source which generates a second ion having asmaller charge-to-mass ratio than a charge-to-mass ratio of the firstion, a pre-accelerator having the capability to enable to accelerateboth the first ion and the second ion, a low-energy beam transport linewhich is constituted in such a way to inject either the first ion or thesecond ion into the pre-accelerator, and a post-accelerator of aself-focusing type which accelerates only the first ion afteracceleration which is emitted from the pre-accelerator.
 2. Thesynchrotron injector system according to claim 1, wherein thepost-accelerator is constituted in such a way for both the first ion andthe second ion to be injected and in a case where the first ion isinjected, an acceleration operation is performed and in a case where thesecond ion is injected, an acceleration operation is not performed. 3.The synchrotron injector system according to claim 2, wherein a beamdiameter of the post-accelerator is larger than a beam diameter of thepre-accelerator.
 4. The synchrotron injector system according to claim1, further comprising a distributor, wherein in a case where an ionwhich is emitted from the pre-accelerator is the first ion, the firstion is injected into the post-accelerator and in a case where an ionwhich is emitted from the pre-accelerator is the second ion, the secondion is not injected into the post-accelerator but is emitted from thesynchrotron injector system by the distributor.
 5. The synchrotroninjector system according to claim 1, wherein the pre-acceleratorcomprises a front-stage accelerator which bunches ions which areinjected and a back-stage accelerator which accelerates ions which areinjected by the front-stage accelerator.
 6. The synchrotron injectorsystem according to claim 1, wherein the first ion is a proton and thesecond ion is a carbon ion.
 7. An operation method of a synchrotroninjector system, which injects an ion into a synchrotron, comprising afirst ion source which generates a first ion, a second ion source whichgenerates a second ion having a smaller charge-to-mass ratio than acharge-to-mass ratio of the first ion, a pre-accelerator having thecapability to enable to accelerate both the first ion and the secondion, a low-energy beam transport line which is constituted in such a wayto inject either the first ion or the second ion into thepre-accelerator, and a post-accelerator of a self-focusing type whichaccelerates an ion after acceleration which is emitted from thepre-accelerator, wherein in a case where an ion which is injected intothe post-accelerator is the first ion, an acceleration operation isperformed and in a case where an ion which is injected into the postaccelerator is the second ion, an acceleration operation is notperformed.
 8. The operation method of a synchrotron injector systemaccording to claim 7, wherein the first ion is a proton and the secondion is a carbon ion.